1. Field of the Invention
The present invention relates to an ink tank, and, more particularly, to an ink tank with features to regulate bubbling pressure, so as to accommodate high ink flow rates at a desirable backpressure.
2. Description of the Related Art
An ink jet printer forms an image on a print medium, such as paper, by applying ink on the print medium. The ink may be contained in one or more replaceable supply cartridges. Examples of such replaceable supply cartridges include a replaceable ink tank and a replaceable ink jet printhead cartridge. A replaceable ink jet printhead cartridge, for example, includes both an ink tank and an ink jet micro-fluid ejection device, i.e., a printhead, in a unitary package. In contrast, a replaceable ink tank does not include the micro-fluid ejection device, but rather, the micro-fluid ejection device forms part of a printhead assembly that is separately attached to the printhead carrier.
A typical ink tank includes a free ink chamber separated by a dividing wall from a suspended ink chamber, which is also sometimes referred to as a felt chamber. The felt chamber has inserted therein the felt ink suspending member having pores for retaining ink. The divider wall between the free ink chamber and the felt chamber has an ink communication port, sometimes referred to in the art as a “bubbler window”, to allow transfer of air and ink between the two chambers. The term “bubbling” refers to the process of air and liquid exchange through the ink communication port, i.e., the bubbler window. Air enters the free ink chamber, which in turn allows ink from the free ink chamber to move into the felt chamber.
Bubbling pressure is the pressure at which an air and liquid exchange occurs through the ink communication port, i.e., bubbler window. In prior art ink tanks, the felt in the felt chamber dictates the bubbling pressure. For example, the bubbling pressure is dependant upon the porosity of the felt, erg., the length through which the ink must travel before reaching the wick that transfers ink from the ink tank to the printhead assembly, since ink flow resistance increases as length increases, and vice-versa. Thus, the bubbling pressure has been difficult to regulate with any consistency.